The present invention relates generally to fiber optic cables and, more particularly, to fiber optic drop cables.
Fiber optic cables include optical fibers that are capable of transmitting voice, video, and data signals. Fiber optic cables have advantages over electrical voice, video and data signal carriers, for example, increased data capacity. As businesses and households demand increased data capacity, fiber optic cables can eventually displace electrical voice, video, and data signal carriers. This demand will require low fiber count optical cables to be routed to end users, for example, businesses and households.
Fiber optic cables can typically be used in various applications. For example, fiber optic drop cables may be suitable for both aerial and buried cable applications. More specifically, a fiber optic drop cable may be strung between poles and/or buried in the ground before reaching the end user. Aerial and buried cable environments have unique requirements and considerations. Optical fiber drop cables can meet the unique requirements and considerations of both environments, yet still remain cost effective.
In addition to being cost effective, cables should be simple to manufacture. An example of a low fiber count optical cable manufactured in one step and having optical fibers disposed longitudinally to the cable axis is disclosed in U.S. Pat. No. 5,115,485. An optical fiber is disposed within an electrically conductive strength member that is surrounded and embedded in an elastomeric material that forms the outer jacket. The cable also includes optical fibers embedded in the elastomeric material that forms the outer jacket. This known fiber optic cable has several disadvantages. For example, because the optical fiber is surrounded by the electrically conductive strength member, it is difficult to access the fiber. Moreover, accessing the central optical fiber may result in damage to the embedded optical fibers. Additionally, the embedded optical fibers are coupled to the elastomeric material that forms the outer jacket. Consequently, when the elastomeric outer jacket is stressed, for example, during bending, tensile and compressive stresses can be transferred to the optical fibers, thereby degrading optical performance.
Moreover, fiber optic cables that are strung between poles can carry a tensile load. An example of a fiber optic cable designed to carry a tensile load is disclosed in U.S. Pat. No. 4,422,889. This known cable is an optical fiber cable with a generally cylindrical central support member having helical grooves for carrying optical fibers. During manufacture, the grooves require partial filling with a viscous filling compound, placing the optical fiber in the partially filled groove, and topping off the partially filled groove with further viscous filling compound. Although this known fiber optic cable is designed to prevent the application of tensile stress to the optical fibers by allowing the fibers to sink deeper into the grooves when axially loaded, this design has several disadvantages. For example, from a manufacturing standpoint, it can be more difficult and expensive to form helical grooves and place the optical fibers in helical grooves.
Optical fiber cables are also used in military applications, for example, guidance systems for missiles. An example of a fiber optic cable designed for military applications is disclosed in U.S. Pat. No. 4,786,138. This known cable is designed to be reliable, rugged and difficult to detect, however to achieve these characteristics the cable requires an expensive metal-free material.
Aerial optical fiber sables can also be installed adjacent to installed power transmission systems, an example is disclosed in U.S. Pat. No. 4,786,138. This known cable requires an all-dielectric design for use near power lines. The core includes a slot that houses the optical fibers and a filling compound. The slot requires sealing with a closure cap. A binder is helically wrapped around the core and cap assembly to hold the cap in place. The core and cap assembly is then enclosed with an extruded sheath. This known fiber optic cable has several disadvantages. For example, the cable has multiple components that require multiple manufacturing and assembly steps, which in turn increases cable costs.
One aspect of the present invention provides a fiber optic cable having at least one optical fiber component disposed within at least one retention area of a support member. The support member includes a metallic material having the retention area generally longitudinally formed therein relative to an axis of the cable. The cable can include a cable jacket, cushioning zone adjacent the optical fiber component, a water-blocking component, an interfacial layer at least partially disposed between an outer surface of the support member and cable jacket and/or at least one tab, extending from the support member, bendable for at least partially covering the retention area.
A second aspect of the present invention provides a fiber optic cable having at least one optical fiber component disposed within at least one retention area of a support member. Disposed adjacent the optical fiber component is a cushioning zone to decouple the optical fiber component from the support member. The support member is formed of a metallic material having the retention area disposed substantially parallel and in about a generally fixed position relative to the longitudinal axis of the cable. A water-blocking component is partially disposed within the retention area. An interfacial layer at least partially disposed between an outer surface of the support member and a cable jacket. The cable jacket substantially surrounds the support member and provides protection. The support member can also have at least one bendable tab for at least partially covering the retention area.
A third aspect of the present invention provides a fiber optic cable having at least one optical fiber component disposed within at least one retention area of a support member. The support member can include a metallic or dielectric material. The support member includes a body and at least one tab, extending from the support member and bendable relative to the body. The at least one tab is bendable to at least partially cover the at least one retention area. The cable can include a cushioning zone, a water-blocking component, interfacial layer and/or a cable jacket.
A fourth aspect of the present invention provides a fiber optic cable having at least one optical fiber component disposed within at least one retention area of a support member. The support member includes a metallic material having the retention area generally longitudinally formed therein relative to an axis of the cable. The cable having a strain of 1.0% or less when a 1,000 lb. tensile force is applied. The cable can include a cable jacket, cushioning zone adjacent the optical fiber component, a water-blocking component, interfacial layer and/or at least one tab, extending from the support member, bendable for at least partially covering the retention area.